Dynamic microwave-assisted extraction of flavonoids from Herba Epimedii

An apparatus for extraction of flavonoids from Herba Epimedii has been constructed which utilizes a microwave technique for heating in a dynamic mode. A TM010 microwave resonance cavity was applied to concentrate the microwave energy; the power needed to achieve efficient extraction was significantly reduced. The method has been compared with other extraction methods, such as pressurized microwave-assisted extraction (PMAE), ultrasonic extraction (UE), heat reflux extraction (RE) and Soxhlet extraction (SOX). The four flavonoids in extract were identified by HPLC-MS. The influence of extraction parameters on the extraction yield of flavonoids has been evaluated by comparison with the peak areas of HPLC-DAD spectra in the different extraction methods. The results showed that the extraction yield of flavonoids in Herba Epimedii obtained by dynamic microwave-assisted extraction (DMAE) was higher than that obtained by UE, RE and SOX, and the extraction time is dramatically reduced. The extraction yield obtained by DMAE is similar to that obtained by PMAE. But the flavonoids in Herba Epimedii would not decompose easily when increasing the extraction time in DMAE. This is the benefit of dynamic extraction system which can transfer the analytes extracted from the sample matrix with flowed fresh solvent to the out of extraction vessel. (C) 2007 Elsevier B.V. All rights reserved.